Journal ofNeurology, Neurosurgery, and Psychiatry 1992;55:12-15

Visual field defects in vascular lesions of thelateral geniculate body

Cristian Luco, Arnold Hoppe, Mariana Schweitzer, Ximena Vicufia, Aldo Fantin

Department ofNeurology, School ofMedicine, UniversidadCat6lica de Chile,SantiagoC LucoA HoppeA FantinDepartment ofNeurology, School ofMedicine, Universidadde Chile, and Neuro-Ophthalmology Unit,Instituto deNeurocirugia,Santiago, ChileC LucoM SchweitzerX VicufiaCorrespondence to:Dr Luco, Department ofNeurology, UniversidadCat6lica de Chile, Marcoleta387, Santiago, ChileReceived 4 October 1990 andin revised form 7 March1991.Accepted 26 March 1991

AbstractCorresponding retinal nerve fibres begintheir path in the eyes and end in a singlevisual cortical cell. Because of thisarrangement, lesions in the anteriorvisual pathway produce incongruentvisual field defects and in the posteriorpathway congruent field defects. Thelateral geniculate body is on the anteriorthird of the visual pathway. A lesion ofthis nucleus produces moderately tocompletely congruent visual fielddefects. Five patients with ischaemiclesions of the lateral geniculate body arereported. Two patients had a wedge-shaped homonymous hemianopia, twoother cases had congruent superiorhomonymous quadrantic defects and thefifth a quadruple sector defect. Thelateral geniculate body has a dual bloodsupply from the anterior choroidalartery (branch from internal carotidartery) and from the lateral choroidalartery (branch from the posteriorcerebral artery). A schematic diagramhas been devised which shows that aknowledge of the visual field disruptedcan identify the arterial system involved.

The fibres of the visual pathway that carryinformation from the retina to the calcarinecortex have a systematic spatial arrangement.Lesions in this pathway produce characteristicvisual field defects whose analysis frequentlyallows localisation of the lesion, especially inthe anteroposterior axis. One of the mostfrequently used features in diagnosis is con-gruency-that is, the similarity between thevisual field defect of one eye and the other.Congruency is maximal in cortical lesions and

Figure Wedge-shaped, right homonymous hemianopia. Case 1.

minimal in optic tract lesions.' A vascularlesion of the lateral geniculate body (LGB) isan exception to the relationship between con-gruency of the visual field defect and theanteroposterior localisation. Even though theLGB is on the anterior third of the retrochias-matic visual pathway and a lesion just in frontor behind this nucleus produces incongruentfield defects, the visual field defect found inthese cases is a congruent wedge-shapedhomonymous hemianopia or the sparing of asymmetrical wedge-shaped area, and loss ofupper and lower quadrants. These visual fielddefects are infrequent in lesions in other sitesof the visual pathway and anatomically almostimpossible in a vascular lesion of the visualcortex. Another type of field defect found withLGB lesions is congruent quadrantic contrac-tion of the upper or lower visual field.2Lesions of this nucleus are infrequent and theuse of CT enables a more accurate diagnosis.We report on five patients with vascular

lesions of the LGB. Two had the typicalwedge-shaped homonymous hemianopia, twoother cases had superior congruent homo-nymous quadrantic defects (quadrantanopsia)and the last one a quadruple sectoranopia. Infour cases CT scan revealed a vascular lesionof the LGB and in one case the test wasnegative.

Case reportsCase 1This patient was a 62 year old male with anunremarkable past medical history. InDecember 1986 he had a severe headache and"visual disturbance". On examination, a fewhours later the only abnormality was highblood pressure (160/100 mm Hg). Theneurological examination was normal exceptfor the visual fields. The neurophthalmo-logical examination showed a normal visualacuity, pupillary reaction, ocular motility andocular fundus. A right congruent, wedge-shaped homonymous hemianopia (fig 1) wasdetected. A brain CT scan disclosed anischaemic lesion of the posterolateral area ofthe left thalamus, enhanced by contrast (fig 2).Eight months later the visual field was normal,and the patient had no visual complaints.

Case 2This patient was a 49 year old male withmoderate arterial hypertension, who suddenlynoticed a disturbance of his left visual fieldwith no other general or ophthalmologicalcomplaints. On neurophthalmological

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Visualfield defects in vascular lesions of the lateral geniculate body

Figure 2 Brain CT scanwith a left posterolateralthalamic lesions. Case 1.

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examination his visual acuity was 6/6 in botheyes, the pupil reaction, ocular motility andfundus examination were normal. The visualfield had an incomplete wedge-shaped lefthomonymous hemianopia (fig 3). Theneurological examination was otherwise nor-mal. A second generation CT scan did notdisclose a definite lesion. Based on the visualfield defect and a negative CT scan, anischaemic lesion of the LGB was suggested.

Case 3This patient was a 71 year old female with aclinical history of pulmonary tuberculosis,moderate arterial hypertension and cardiacarrythmia due to an auricular flutter. Herpresent illness began suddenly one night withtachycardia followed by significant polyuriaand a mild left hemiparesis of sudden onset.On examination, a few hours later, the bloodpressure was 150/90, with normal cardiacrhythm. On neurological examination she hada mild left sensory motor deficit. Neur-ophthalmological examination showed rightvisual acuity 6/18 and left 6/12, with normal

pupil reactions and eye movements. The fun-dus examination revealed a tilted disc withatrophy of peripapillary pigment epithelium.The contrast enhanced brain CT scan showeda right thalamic and inferotemporal (hip-pocampus) ischaemic lesion (fig 4). The visualfield disclosed a congruent left superiorquadrantic defect (fig 5). Six months later thevisual field had returned to normal.

Case 4This patient was a 56 year old male with a twoyear history of gastrectomy for a peptic ulcer,without arterial hypertension or diabetesmellitus, who, after bending down, experi-enced a slight dizziness and a strange visualfeeling. General and neurological examinationwere normal. Neurophthalmological examina-tion showed normal visual acuity, pupillaryreaction, ocular motility and fundus. On visualfield examination there was a congruent leftsuperior quadrantanopsia (fig 6). Brain CTscan showed a right posterolateral thalamicinfarct (fig 7). A year later, the neurophthal-mological control was normal and CT scanrevealed a small hypodense lesion of the samearea.

Case SThis patient was a 56 year old woman withchronic arterial hypertension who had beentreated with propranolol and diuretics. Hercurrent illness began with a sudden onset righthemiparesis and a right visual field deficit. Ongeneral examination her blood pressure was130/90, with no other abnormality. Onneurological examination there was a mild righthemiparesis and a right visual field defect onconfrontation. The hemiparesis partiallyrecovered in four hours, but the field defectshowed no change. A brain CT on admissionwas normal. The neurophthalmologicalexamination two days later showed normalvision in both eyes, with normal ocular

Figure 3 Wedge-shaped, left homonymous hemianopia. Case 2.

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Figure 4 Brain CT scan with a right thalamic andinferotemporal ischaemic lesion. Case 3.

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Luco, Hoppe, Schweitzer, Vicufia, Fantin

Figure 5 Left superior quadrantopsia. Case 3.

motility, pupillary light reaction and ocularfundus. Her visual field revealed a rightsuperior and inferior homonymous quandran-tic defect with sparing of a wedge-shaped areasymmetrically located along the horizontalmeridian (fig 8). A second CT carried out fivedays later showed a left basal temporal lobeischaemic lesion (fig 9). Four vessel cerebralangiograms were normal.

DiscussionThe arrangement of the nerve fibres along thevisual pathway enables us to have a single brainimage because retinal receptors, which receivein each eye the same external stimuli, reach acommon cortical cell. The fibres of these corre-sponding retinal points begin their voyage 6cms wide apart. As they proceed towards theoccipital pole of the brain they approach eachother and become paired as they reach thevisual cortex. A discrete lesion in the posteriorportion of the visual pathway has a highpossibility of curtailing information comingfrom corresponding retinal points resulting incongruent visual field defects. The same dis-crete lesion in the anterior part of the pathway(optic tract) may affect fibres coming fromdifferent retinal areas producing incongruentfield defects.

The LGB is a wedge-shaped structuresituated at the posterolateral aspect of thethalamus, which receives information from thesecond neuron of the visual pathway. Fibresfrom the ipsilateral retina end in layers 2, 3 and5 and those from the contralateral retina inlayers 1, 4 and 6, without interaction betweenthem. The LGB is on the anterior third of theretrochiasmatic visual pathway receiving theoutput of the optic tract. Different authors34have suggested that visual field defects inpatients with LGB lesions are incongruent.However, when analysing the literature, as wellas our own cases, we conclude that field defectsin a vascular LGB lesion appear to havemoderate to complete congruency. This is anexception to the rule that the nearer the lesion isto the calcarine cortex the greater the con-gruency of the visual field defect. On analysingvisual fields this exception should be taken intoaccount, even though LGB lesions are soinfrequent that they are not mentioned inreports of a large series of homonymoushemianopias.5The LGB has a dual blood supply: from the

anterior choroidal artery (branch ofthe internalcarotid artery) and from the lateral choroidalartery (branch of the posterior cerebral artery).Frisen et al6 have reported two patients with awedge-shaped congruent homonymous hemi-anopia showing that the lesion was due to anocclusion of the lateral choroidal artery. Thesame author7 reported another patient with asuperior and inferior homonymous defectwhich he called a quadruple sectoranopia.Cerebral angiography revealed an occlusion ofthe distal portion of the anterior choroidalartery and normal lateral choroidal artery.Schacklett et al8 have presented an elegantscheme of the projection of the visual field onthe LGB. They reported two patients with awedge-shaped homonymous hemianopia, onewith a congruent defect and another that wasincongruent. The patient with the congruent

Figure 6 Left superior quadrantopsia. Case 4.Figure 7 Brain CT scan with a right posterolateralthalamic lesion. Case 4.

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Visualfield defects in vascular lesions of the lateral geniculate body

Figure 8 Right quadruple sectoranopia. Superior and inferior quadrantic defects withsparing of a central wedge-shaped area. Case 5.

defect had an ischaemic lesion of the LGBproduced by an arteriovenous malformation ofthe lateral choroidal artery.From this evidence we have devised a

schematic diagram (fig 10) in which knowingthe area of the visual field disrupted, we canconclude, within limits, which LGB arterialsystem is occluded-anterior choroidal orlateral choroidal artery. Two of our patientspresented with typical wedge-shaped homo-nymous hemianopia and even though one had anegative CT scan (probably due to its lowsensitivity), we believe that in both cases thesame territory, that is, the area served by thelateral choroidal artery, was involved. Twoother patients had a congruent superiorhomonymous quadrantic defect. One had aninfarct of the area of the anterior choroidalartery, while the other had an ischaemic lesionof the LGB but the arterial territory involvedcould not be defined. The fifth patient had asuperior and inferior quadrantic defect withsparing of the area just above and below the

90

cmIIJ]hII Lateral choroidal artery Anterior choroidal artery

Figure 10 Area of visualfield disrupted by occlusion of the anterior or lateralchoroidal artery.

Figure 9 Brain CT scan with a left basal temporal lobeischaemic lesion. Case 5.

horizontal meridian-the sector defect ofFrisen-and the CT scan showed an ischaemiclesion of the territory supplied by the anteriorchoroidal artery.

In a patient with a history of a brain vascularlesion the finding of a typical wedge-shapedcongruent homonymous hemianopia stronglysuggests an ischaemic lesion of the LGBinvolving the lateral choroidal artery. Conver-sely, if the patient has a quadruple sector-anopia7 or a superior congruent homonymousquadrantic defect and a thalamic infarct, it islikely that there has been an ischaemic lesioninvolving the anterior choroidal artery. When anon cardiogenic embolic infarct is suspected, itis important to determine whether theischaemia affects the anterior or posteriorcerebral circulation as a different approach toinvestigation is adopted to each.

1 Harrington DO. In: The Visual Fields. 2nd edn. Saint Louis;Mosby CV. 1964:134.

2 Mohr JP, Leicester J, Stoddard T, Sidman M. Righthemianopia with memory and color deficits in circum-scribed left posterior cerebral artery territory infarction.Neurology 1971;21:1104-13.

3 Gunderson CH, Hoyt WF. Geniculate hemianopia: incon-gruous homonymous field defect in two patients withpartial lesion of the lateral geniculate nucleus. J NeurolNeurosurg Psychiatry 1971;34:1-6.

4 Balado M, Malbran J, Franke E. Incongruencia hemian-opica derecha por lesion primitiva del cuerpo geniculadolateral izquierdo (isoptera internas). Arch Arg Neurol1934;11:143-59.

5 Smith JL. Homonymous hemianopia: A review of onehundred cases. Am J Ophthalmol 1962;54:616-22.

6 Frisen L, Holmegaard L, Rosencrantz M. Sectorial opticatrophy and homonymous horizontal sectoranopia. Alateral choroidal artery syndrome? J Neurol NeusosurgPsychiatry 1979;42:590-4.

7 Frisen L. Quadruple sectoranopia and sectorial opticatrophy: A syndrome of the distal anterior choroidalartery. J Neurol Neurosurg Psychiatry 1979;42:590-4.

8 Shacklett D, O'Connor P, Dormant CN, Linn D, Carter J.Congruous and incongruous sectorial visual defects withlesions of the lateral geniculate nucleus. Amer J Ophthal-mol 1984;98:283-90.

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